Thioacetate Functionalized Isobutylene-Based Polymers and Curable Compositions Containing the Same

ABSTRACT

Provided herein are thioacetate isobutylene-based polymer compositions comprising thioalkylated functionalized polymer, and a sulfur donor and/or accelerator cure system. The thioalkylated functionalized polymer is produced via nucleophilic substitution reaction in solution. The present thioacetate functionalized isobutylene-based polymer compositions together with various accelerators and sulfur donors can form thermosets useful for pharmaceutical and tire applications without the use of zinc or a zinc oxide activator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This invention claims priority to and the benefit of U.S. Ser. No.62/651,972, filed Apr. 3, 2018 and EP Application No. 18172742.1, filedMay 16, 2018, which are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

The present disclosure generally relates to functionalizedisobutylene-based polymers useful in curable compositions, and moreparticularly relates to thioalkylated functionalized isobutylene-basedpolymers and curable compositions containing the same.

BACKGROUND OF THE INVENTION

Curing isobutylene-based elastomers is generally more complex than thatfor general-purpose rubbers. Powers, K. W. et al., FunctionalizedCopolymers of Para-AlkylStyrene/Isoolefin Prepared by NucleophilicSubstitution, CA 2009681. For example, while isobutylene co-para-methylstyrene elastomer compositions provide improved permeabilitycharacteristics for end products, use ofpoly(isobutylene-co-para-methylstyrene) compositions (referred to hereinas “BIMSM”) have drawbacks when compared to other butyl-basedcompositions. These drawbacks include a limited cure versatility.

Further, regardless of the cure system, vulcanization rates betweenadjacent components must be similar in the isobutylene-based polymercomposition. With otherwise superior mechanical properties, incompatiblecure rates of the various polymers in the isobutylene-based rubbercomposition can cause separation of the composite because goodinterfacial adhesion is not created during crosslinking and cure of theelastomer composition.

While the selection of a specific cure system is a function of thepolymer type and the specific in-service requirements of the thermosetproduct, cure systems used for isobutylene-based elastomers are oftensulfur-based with the use of metal oxides such as zinc oxide systems.Moreover, because the backbone of isobutylene-based elastomers arehighly saturated, ultra-fast accelerators are required for efficientvulcanization. Many ultra-fast accelerators are nitrosamine generatorsand use of such accelerators is not recommended.

Further, vulcanization chemistry for the numerous types ofisobutylene-based polymers can vary. For example, because of the absenceof carbon-carbon double bonds in the backbone and the presence of thereactive benzylic bromide, the vulcanization chemistry for BIMSM differsfrom that of other isobutylene-based elastomers. See, S. Solis, et al.,How to Pick Proper Model Vulcanization Systems: Part 2 of 2, RubberWorld, Jul. 9, 2007. Brominated poly(isobutylene-co-para-methylstyrene)will not sufficiently crosslink with sulfur donor or sulfur/sulfur donorsystems alone. As such, crosslinking of BIMSM generally involvesformation of carbon-carbon bonds via a Friedel-Crafts alkylationreaction catalyzed by zinc halides.

Stearic acid functions as an accelerator of BIMSM vulcanization. Zincstearate formed as a product of the reaction between zinc oxide andstearic acid can react with BIMSM and displace benzylic bromine. Asreported, in the absence of stearic acid, cure rates are very low.

A need exists, therefore, for functionalized isobutylene-based polymerswhich can form thermosets with common accelerators and sulfur donors,and without the use of zinc salts or a zinc oxide activator.

SUMMARY OF THE INVENTION

Provided herein are thioacetate isobutylene-based polymer compositionscomprising thioalkylated functionalized polymer, and a sulfur donorand/or accelerator cure system. In an aspect, the functionalized polymeris thioacetate functionalized poly(isobutylene-co-para-methylstyrene).The thioacetate isobutylene-based polymer composition can furthercomprise at least one filler. In an aspect, the filler is selected fromthe group of carbon black, white filler and/or mixtures thereof. In anaspect, the sulfur donor is selected from the group consisting oftetramethyl thiuram disulfide (“TMTD”), 4,4′-dithiodimorpholine,dipentamethylene thiuram tetrasulfide (“DPTT”), and thiocarbamylsulfonamide. In an aspect, the accelerator cure system comprises one ormore of thiazoles, amines, guanidines, sulfenamides, thiurams,dithiocarbamates, and/or zanthates. In an aspect, the accelerator curesystem is N-cyclohexyl-2-benzothiazole sulfenamide (“CBS”) ordiphenylguanidine.

Also, provided herein are zinc-free thermoset compositions comprisingthioalkylated functionalized polymer, and a sulfur donor and/oraccelerator cure system. In an aspect, the functionalized polymer isthioacetate functionalized poly(isobutylene-co-para-methylstyrene). Thezinc-free thermoset composition can further comprise at least onefiller. In an aspect, the filler is selected from the group of carbonblack, white filler and/or mixtures thereof. In an aspect, the sulfurdonor is selected from the group consisting of tetramethyl thiuramdisulfide (“TMTD”), 4,4′-dithiodimorpholine, dipentamethylene thiuramtetrasulfide (“DPTT”), and thiocarbamyl sulfonamide. In an aspect, theaccelerator cure system comprises one or more of thiazoles, amines,guanidines, sulfenamides, thiurams, dithiocarbamates, and/or zanthates.In an aspect, the accelerator cure system isN-cyclohexyl-2-benzothiazole sulfenamide (“CBS”) or diphenylguanidine.As used herein the term “zinc-free composition” refers to a composition“substantially free of zinc,” or in other terms having less than 0.01 wt% zinc based on the total weight of the composition.

Further provided herein are rubber compositions comprising thioalkylatedfunctionalized polymer, and a sulfur donor and/or accelerator curesystem. In an aspect, the functionalized polymer is thioacetatefunctionalized poly(isobutylene-co-para-methylstyrene). The rubbercomposition can further comprise at least one filler. In an aspect, thefiller is selected from the group of carbon black, white filler and/ormixtures thereof. In an aspect, the sulfur donor is selected from thegroup consisting of tetramethyl thiuram disulfide (“TMTD”),4,4′-dithiodimorpholine, dipentamethylene thiuram tetrasulfide (“DPTT”),and thiocarbamyl sulfonamide. In an aspect, the accelerator cure systemcomprises one or more of thiazoles, amines, guanidines, sulfenamides,thiurams, dithiocarbamates, and/or zanthates. In an aspect, theaccelerator cure system is N-cyclohexyl-2-benzothiazole sulfenamide(“CBS”) or diphenylguanidine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph depicting the H¹ NMR spectroscopy of the modifiedpoly(isobutylene-co-para-methylstrene), as described in Example 1.

FIG. 2 is the MDR cure profile of BIMSM versus thioacetatefunctionalized poly(isobutylene-co-para-methylstyrene) with a TMTDcurative.

FIG. 3 is the MDR cure profile of BIMSM versus thioacetatefunctionalized poly(isobutylene-co-para-methylstyrene) with a DPTTcurative.

FIG. 4 is the MDR cure profile of thioacetate functionalizedpoly(isobutylene-co-para-methylstyrene) with varying levels of TMTDcurative.

FIG. 5 is the MDR cure profile of thioacetate functionalizedpoly(isobutylene-co-para-methylstyrene) versus BIMSM with CBS and DPGaccelerators.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various specific embodiments, versions and examples are describedherein, including exemplary embodiments and definitions that are adoptedfor purposes of understanding the claimed invention. While the followingdetailed description gives specific preferred embodiments, those skilledin the art will appreciate that these embodiments are exemplary only,and that the invention can be practiced in other ways. For purposes ofdetermining infringement, the scope of the invention will refer to anyone or more of the appended claims, including their equivalents, andelements or limitations that are equivalent to those that are recited.Any reference to the “invention” may refer to one or more, but notnecessarily all, of the inventions defined by the claims.

All numerical values within the detailed description and the claimsherein are modified by “about” or “approximately” the indicated value,taking into account experimental error and variations.

For the purposes of this disclosure, the following definitions willapply:

As used herein, the term “alkyl” refers to a paraffinic hydrocarbongroup which may be derived from an alkane by dropping one or morehydrogens from the formula, such as, for example, a methyl group (CH₃),or an ethyl group (CH₃CH₂).

The term “elastomer” may be used interchangeably with the term “rubber”and refers to any composition comprising at least one elastomer.

The term “rubber” refers to any polymer or composition of polymersconsistent with the ASTM D1566 definition: “a material that is capableof recovering from large deformations, and can be, or already is,modified to a state in which it is essentially insoluble (but can swell)in boiling solvent”.

As used herein, the term “rubber” includes, but is not limited to, atleast one or more of brominated butyl rubber, chlorinated butyl rubber,star-branched polyisobutylene rubber, star-branched brominated butyl(polyisobutylene/isoprene copolymer) rubber; halogenatedpoly(isobutylene-co-p-methylstyrene), such as, for example, terpolymersof isobutylene derived units, p-methylstyrene derived units, andp-bromomethylstyrene derived units (BrIBMS), and the like halomethylatedaromatic interpolymers as in U.S. Pat. Nos. 5,162,445, 4,074,035, and4,395,506; halogenated isoprene and halogenated isobutylene copolymers,halogenated terpolymer of isobutylene/isoprene/para-alkylstyrene,polychloroprene, and the like, and mixtures of any of the above.Halogenated rubbers are also described in U.S. Pat. Nos. 4,703,091 and4,632,963.

The term “phr” refers to parts per hundred rubber and is a measure ofthe component of a composition relative to 100 parts by weight of theelastomer (rubber component) as measured relative to total elastomer.The total phr (or parts for all rubber components, whether one, two,three, or more different rubber components) is always defined as 100phr. All other non-rubber components are a ratio of the 100 parts ofrubber and are expressed in phr.

The term “isoolefin” refers to a C₄ to C₇ compound and includes, but isnot limited to, isobutylene, isobutene 2-methyl-1-butene,3-methyl-1-butene, 2-methyl-2-butene, and 4-methyl-1-pentene. Themultiolefin is a C₄ to C₁₄ conjugated diene such as isoprene, butadiene,2,3-dimethyl-1,3-butadiene, myrcene, 6,6-dimethyl-fulvene,cyclopentadiene, hexadiene and piperylene. An exemplary polymer can beobtained by reacting 92 to 99.5 wt % of isobutylene with 0.5 to 8 wt %isoprene, or reacting 95 to 99.5 wt % isobutylene with from 0.5 to 5.0wt % isoprene.

The term “substituted” refers to at least one hydrogen group beingreplaced by at least one substituent selected from, for example, halogen(chlorine, bromine, fluorine, or iodine), amino, nitro, sulfoxy(sulfonate or alkyl sulfonate), thiol, alkylthiol, and hydroxy; alkyl,straight or branched chain having 1 to 20 carbon atoms which includesmethyl, ethyl, propyl, isopropyl, normal butyl, isobutyl, secondarybutyl, tertiary butyl, and the like; alkoxy, straight or branched chainalkoxy having 1 to 20 carbon atoms, and includes, for example, methoxy,ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, secondary butoxy,tertiary butoxy, pentyloxy, isopentyloxy, hexyloxy, heptyloxy, octyloxy,nonyloxy, and decyloxy; haloalkyl, which means straight or branchedchain alkyl having 1 to 20 carbon atoms which is substituted by at leastone halogen, and includes, for example, chloromethyl, bromomethyl,fluoromethyl, iodomethyl, 2-chloroethyl, 2-bromoethyl, 2-fluoroethyl,3-chloropropyl, 3-bromopropyl, 3-fluoropropyl, 4-chlorobutyl,4-fluorobutyl, dichloromethyl, dibromomethyl, difluoromethyl,diiodomethyl, 2,2-dichloroethyl, 2,2-dibromoethyl, 2,2-difluoroethyl,3,3-dichloropropyl, 3,3-difluoropropyl, 4,4-dichlorobutyl,4,4-dibromobutyl, 4,4-difluorobutyl, trichloromethyl, trifluoromethyl,2,2,2-trifluoroethyl, 2,3,3-trifluoropropyl, 1,1,2,2-tetrafluoroethyl,and 2,2,3,3-tetrafluoropropyl. Thus, for example, a “substitutedstyrenic unit” includes p-methylstyrene, and p-ethylstyrene, and thelike.

As used herein, the term isobutylene-based polymer composition can bereferred to as a “butyl-based composition,” a “butyl-based elastomercomposition,” a “butyl-based polymer composition,” and/or an“isobutylene-based elastomer composition.” The terms “isobutylene-basedelastomer” and “isobutylene-based polymer” can be used interchangeablyand each refers to polymers comprising a plurality of repeat units fromisobutylene. “Isobutylene-based elastomer” or “isobutylene-basedpolymer” refers to elastomers or polymers comprising at least 70 molepercent repeat units from isobutylene.

As described herein, rubber can be a halogenated rubber or halogenatedbutyl rubber such as brominated butyl rubber or chlorinated butylrubber. General properties and processing of halogenated butyl rubbersis described in THE VANDERBILT RUBBER HANDBOOK 105-122 (R. F. Ohm ed.,R. T. Vanderbilt Co., Inc. 1990), and in RUBBER TECHNOLOGY 311-321(1995). Butyl rubbers, halogenated butyl rubbers, and star-branchedbutyl rubbers are described by E. Kresge and H. C. Wang in 8 KIRK-OTHMERENCYCLOPEDIA OF CHEMICAL TECHNOLOGY 934-955 (John Wiley & Sons, Inc. 4thed. 1993).

The butyl rubber can be halogenated in hexane diluent at from 40 to 60°C. using bromine (Bra) or chlorine (Cl₂) as the halogenation agent. Thehalogenated butyl rubber has a Mooney viscosity of from 20 to 70 (ML 1+8at 125° C.), or from 25 to 55. The halogen content is from 0.1 to 10 wt% based in on the weight of the halogenated butyl rubber or from 0.5 to5 wt %. The halogen wt % of the halogenated butyl rubber is from 1 to2.2 wt %.

As used herein, “halogenated butyl rubber” refers to both butyl rubberand “star-branched” butyl rubber. The halogenated rubber can be ahalogenated copolymer of a C₄ (as noted sometimes as “C4”) to C₇ (alsonoted sometimes as “C7”) isoolefin and a multiolefin. The halogenatedrubber component can be a blend of a polydiene or block copolymer, and acopolymer of a C₄ to C₇ isoolefin and a conjugated, or a “star-branched”butyl polymer. The halogenated butyl polymer can be described as ahalogenated elastomer comprising C₄ to C₇ isoolefin derived units,multi-olefin derived units, and halogenated multiolefin derived units,and includes both “halogenated butyl rubber” and so called “halogenatedstar-branched” butyl rubber.

Halogenated butyl rubber can be produced from the halogenation of butylrubber. Halogenation can be carried out by any means, and the inventionis not herein limited by the halogenation process. Methods ofhalogenating polymers such as butyl polymers are disclosed in U.S. Pat.Nos. 2,631,984, 3,099,644, 4,554,326, 4,681,921, 4,650,831, 4,384,072,4,513,116 and 5,681,901. Preferably, the olefin polymerization feedsemployed in producing halogenated butyl rubber include those olefiniccompounds conventionally used in the preparation of butyl-type rubberpolymers. The butyl polymers are prepared by reacting a co-monomermixture, the mixture having at least one (1) C₄ to C₇ isoolefin monomercomponent such as isobutylene with (2) a multi-olefin, or conjugateddiene, monomer component. The isoolefin can be in a range from 70 to99.5 wt % by weight of the total comonomer mixture, or 85 to 99.5 wt %.The conjugated diene component is present in the comonomer mixture from30 to 0.5 wt % or from 15 to 0.5 wt %. From 8 to 0.5 wt % of theco-monomer mixture is conjugated diene.

As used herein, EXXPRO® refers to a brominated isobutylene-co-paramethyl styrene (BIMSM) rubber or isobutylene-co-para-methyl-styrenebased elastomer, produced by catalytic polymerization of isobutylene andisoprene and manufactured by ExxonMobil useful in a variety of consumerapplications including tires and medical tube stoppers.

As used herein, the term “bromobutyl” or “bromobutyl polymer” refers tobrominated isobutylene-isoprene or brominated isobutylene-isoprenerubber (“BIIR”) as manufactured by ExxonMobil Chemical, a family ofbutyl rubbers used in a variety of consumer applications including tiresand various medical applications.

In an aspect, an exemplary halogenated butyl rubber is Bromobutyl 2222(ExxonMobil Chemical Company). Bromobutyl 2222, also known as BIIR 2222,refers to a brominated copolymer of isobutylene and isoprene having aspecific gravity of 0.93; a Mooney viscosity target of 32, a minimum of28, and a maximum of 36; a bromine composition target of 1.03%, aminimum of 0.93%, and a maximum of 1.13%; and a calcium compositiontarget of 0.15%, a minimum of 0.12%, and a maximum of 0.18%. Further,cure characteristics of Bromobutyl 2222 are as follows: MH is from 28 to40 dNm, ML is from 7 to 18 dNm (ASTM D2084, modified).

Another commercial available halogenated butyl rubber is Bromobutyl 2255(ExxonMobil Chemical Company). Its Mooney viscosity is from 41 to 51 (ML1+8 at 125° C., ASTM 1646, modified), and the bromine content is from1.8 to 2.2 wt %. Further, cure characteristics of Bromobutyl 2255 are asfollows: MH is from 34 to 48 dNm, ML is from 11 to 21 dNm (ASTM D2084,modified).

Star-branched halogenated butyl rubber (“SBHR”) is a composition of abutyl rubber, either halogenated or not, and a polydiene or blockcopolymer, either halogenated or not. This halogenation process isdescribed in detail in U.S. Pat. Nos. 4,074,035, 5,071,913, 5,286,804,5,182,333 and 6,228,978. The secondary polymer is not limited by themethod of forming the SBHR. The polydienes/block copolymer, or branchingagents (hereinafter “polydienes”), are typically cationically reactiveand are present during the polymerization of the butyl or halogenatedbutyl rubber or can be blended with the butyl or halogenated butylrubber to form the SBHR. The branching agent or polydiene can be anysuitable branching agent, and the invention is not limited to the typeof polydiene used to make the SBHR.

The SBHR is typically a composition of butyl or halogenated butyl rubberand a copolymer of a polydiene and a partially hydrogenated polydieneselected from the group including styrene, polybutadiene, polyisoprene,polypiperylene, natural rubber, styrene-butadiene rubber,ethylene-propylene diene rubber, styrene-butadiene-styrene andstyrene-isoprene-styrene block copolymers. These polydienes are present,based on the monomer weight percent, greater than 0.3 wt %, or from 0.3to 3 wt % or from 0.4 to 2.7 wt %.

A commercial SBHR is Bromobutyl 6222 (ExxonMobil Chemical Company),having a Mooney viscosity (ML 1+8 at 125° C., ASTM 1646, modified) offrom 27 to 37, and a bromine content of from 2.2 to 2.6 wt % relative tothe SBHR. Further, cure characteristics of Bromobutyl 6222 are asfollows: MH is from 24 to 38 dNm, ML is from 6 to 16 dNm (ASTM D2084,modified)

The term “olefin” refers to a linear, branched, or cyclic compoundcomprising carbon and hydrogen and having a hydrocarbon chain containingat least one carbon-to-carbon double bond in the structure thereof,where the carbon-to-carbon double bond does not constitute a part of anaromatic ring. The term “olefin” is intended to embrace all structuralisomeric forms of olefins, unless it is specified to mean a singleisomer or the context clearly indicates otherwise.

As used herein, a “polymer” has two or more of the same or different“mer” units. A “homopolymer” is a polymer having mer units that are thesame. A “copolymer” is a polymer having two or more mer units which aredifferent from each other. Copolymer means polymers having more than onetype of monomer, including interpolymers, terpolymers, or higher orderpolymers. A “terpolymer” is a polymer having three mer units that aredifferent from each other. “Different” in reference to mer unitsindicates that the mer units differ from each other by at least one atomor are different isomerically. The terms polyolefin and polymer aresometimes used interchangeably herein.

The term “copolymer” refers to random polymers of C₄ to C₇ isoolefinsderived units and alkylstyrene. For example, a copolymer can contain atleast 85% by weight of the isoolefin, about 8 to about 12% by weightalkylstyrene, and about 1.1 to about 1.5 wt % of a halogen. For example,a copolymer can be a random elastomeric copolymer of a C₄ to C₇alpha-olefin and a methylstyrene containing at about 8 to about 12% byweight methylstyrene, and 1.1 to 1.5 wt % bromine or chlorine.Alternatively, random copolymers of isobutylene and para-methylstyrene(“PMS”) can contain from about 4 to about 10 mol % para-methylstyrenewherein up to 25 mol % of the methyl substituent groups present on thebenzyl ring contain a bromine or chlorine atom, such as a bromine atom(para-(bromomethylstyrene)), as well as acid or ester functionalizedversions thereof.

As used herein, comonomers can be linear or branched. Linear comonomersinclude, but are not limited to, ethylene or C₄ to C₈ α-olefins,1-butene, 1-hexene, and 1-octene. Branched comonomers include4-methyl-1-pentene, 3-methyl-1-pentene, and 3,5,5-trimethyl-1-hexene.Comonomers include styrene.

As provided herein, examples of isobutylene-based polymers includeisobutylene-isoprene elastomers such as butyl rubber (“IIR”),halogenated elastomers such as bromobutyl rubber (“BIIR”), chlorobutylrubber (“CIIR”), star branched bromobutyl rubber (“SBB”), and starbranched chlorobutyl (“SBC”) and brominated isobutylenepara-methylstyrene (“BIMSM”). Poly(isobutylene-co-para-methylstyrene)elastomer and brominated poly(isobutylene-co-para-methylstyrene)(“BIMSM”) are currently sold under the trade name of EXXPRO®.

Functionalized polyolefins are functionalized polymers (also referred tosometimes as functionalized olefins) having one or more polar andnonpolar functionalities, i.e., specific groups or moieties of atoms orbonds within the molecules that are responsible for the characteristicchemical reactions of the molecules. The functional group can undergothe same or similar chemical reaction regardless of the size of thepolymer backbone, allowing for systematic prediction of chemicalreactions and polymer behavior as well as design of chemical synthesis.Once functionalized, atoms of the functional groups are typically linkedto each other and the polymer by covalent bonds. The reactivity of afunctional group can be modified by other functional groups nearby.

Randomly functionalized polyolefins have differing types, location andamount of functionality on the polyolefin backbone. Categories offunctionalized polyolefin include randomly functionalized polyolefinsand graft polyolefins. Using a post-functionalization technique, thefunctionality (moiety or chemical group) is attached onto a preexistingpolymer backbone.

Grafting polyolefins with a functional group can deliver an improvementin the properties of the isobutylene-based polymer. As apost-polymerization reaction, grafting methodologies can chemicallymodify the macromolecular backbone of the polyolefin in order tointroduce active sites capable of functionality. In solution,functionalized polymers can be produced by nucleophilic substitutionprocessing. See e.g., Canadian Patent No. 2009681 A1 (where the reactionwas performed in the presence of a solvent). The functionalizedisobutylene-based polymers can then be crosslinked and cured undervarious systems. See e.g., U.S. Publication No. 2016/0108141.

To post-functionalization the polyolefin backbone, the functionality canbe attached onto the backbone via nucleophilic substitution. Asexemplified immediately below, nucleophilic substitution can be carriedout in the presence of a solvent such as THF, toluene or xylene:

Under this process, polymers which can be modified include, but are notlimited to, halogenated isoolefin polymers, halobutyl rubber,star-branched bromobutyl, brominatedpoly(isobutylene-co-para-methylstyrene) (“BIMSM”), and brominatedisobutylene-isoprene-para-methylstyrene terpolymers.

However, as noted above, while brominatedpoly(isobutylene-co-para-methylstyrene) elastomers display manyproperties superior to natural rubber and other isobutylene-basedpolymers, BIMSM cures sufficiently only with the use of zinc salts orZnO. S. Solis, et al., How to Pick Proper Model Vulcanization Systems:Part 2 of 2, Rubber World, Jul. 9, 2007. For example, in many instances,the use of 1 phr of ZnO and 2 phr of stearic acid in a carbon blackfilled BIMSM compound is sufficient to obtain a reasonable cure state.Furthermore, while zinc stearate can cure BIMSM, reversion is minimizedby addition of ZnO. Therefore, BIMSM cure systems which produce avulcanizate with adequate scorch and reversion resistance contain athiazole such as MBTS, sulfur, ZnO and stearic acid. Reportedly, curesystems where zinc is absent will not be effective for BIMSM.

Moreover, isobutylene-based elastomers are highly saturated. Therefore,isobutylene-based elastomers generally require ultra-fast acceleratorssuch as thiurams (“TMTD”) and dithiocarbamates (“ZDMC”) for an effectivecure.

Generally, the development of halogenated butyl rubber has extended theusefulness of butyl-based polymers by providing higher curing rates andenabling co-vulcanization of general purpose rubbers such as naturalrubber and styrene-butadiene rubber. Butyl rubber and halobutyl rubberare high value polymers, because these polymers possess a combination ofproperties, for example, excellent impermeability, good flex, goodweatherability, co-vulcanization with high unsaturation rubbers, in thecase of halobutyl. The combination of properties has aided thedevelopment of more durable tubeless tires with the air retaining innerliner chemically bonded to the body of the tire. U.S. Publication No.2016/0108141, Paragraphs [0005] to [0011].

In addition to tire applications, the good impermeability, weatheringresistance, ozone resistance, vibration dampening, and stability ofhalobutyl rubbers make them good candidates for materials forpharmaceutical stoppers, construction sealants, hoses, and mechanicalgoods.

Like other rubbers, for most applications, halobutyl rubber must becompounded and vulcanized (chemically crosslinked) to yield useful,durable end use products. The selection and ratios of fillers,processing aids, stabilizers, and curatives play important roles in bothhow the compound will process and how the thermoset product will behave.

Elemental sulfur and organic accelerators are widely used to crosslinkbutyl rubber. The low level of unsaturation requires aggressiveaccelerators such as thiuram or thiocarbamates. The vulcanizationproceeds at the isoprene site with the polysulfidic cross links attachedat the allylic positions, displacing the allylic hydrogen. The number ofsulfur atoms per crosslink is between one and four or more. Cure rateand cure state both increase if the diolefin content is increasedresulting in higher degree of unsaturation. Sulfur cross-links havelimited stability at sustained high temperature.

In halobutyl rubber, the existence of allylic halogen allows easiercross-linking than allylic hydrogen due to the fact that halogen is abetter leaving group in nucleophilic substitution reactions.Furthermore, bromobutyl is faster curing than chlorobutyl and has betteradhesion to high unsaturation rubbers.

As provided herein, benzylic bromide is substituted with thioaceatefunctionality to provide crosslinking to proceed effectively withconventional accelerators, sulfur donors as well as sulfur donor/sulfurcure systems, and without zinc or zinc oxide activators. The resultingcure versatility greatly extends the application for variousisobutylene-based polymers. This new chemistry represents a clean,sulfur-free and zinc-free cure system that can be used for highlydemanding application such as pharmaceutical rubber closures as well astire applications.

Unlike the brominated poly(isobutylene-co-para-methylstyrene) that doesnot undergo curing with either sulfur or sulfur donor system, thepresent synthesized isobutylene-based polymers have substitutedthioalkylate groups (substituted for the benzylic bromide) and can formthermosets quickly with various accelerators and sulfur donors, andwithout the use of zinc oxide activator. The chemistry provided hereinrepresents a clean, sulfur-free and zinc-free cure system that is usefulfor highly demanding applications such as pharmaceutical rubber closuresand tire products with the use of EV or semi-EV vulcanization system.

As described in Examples 1, 2, and 3 below, we have prepared a modifiedpoly(isobutylene-co-para-methylstyrene) having a thioacetate as afunctional group via nucleophilic substitution action in a solutionprocess as follows:

The following examples are put forth so as to provide those skilled inthe art with a complete disclosure and description and are not intendedto limit the scope of that which the inventors regard as theirinvention.

Example 1 Preparation of Modified ThioacetatePoly(Isobutylene-Co-Para-Methylstyrene) by Nucleophilic SubstitutionReaction in a Solution Process

In this example, nucleophilic substitution reaction of potassiumthioacetate with butylene-based polymer, EXXPRO™ (NPX 1602, Experimentalproduct from ExxonMobil Chemical), was conducted in a 50 liter glassreactor equipped with a stirrer and chiller. Dry Tetrahydrofuran (THF)(water ppm ≤10 ppm) was prepared by passing 99% THF (Sigma Aldrich)through 3 A molecular sieve. 4000 grams (“gr.”) of EXXPRO™ (Mn=221000g/mole; 5002 g/mole Br; 0.799 mole) was added to the 50 liter reactorunder nitrogen blanket. The butylene-based polymer was dissolved in thealready prepared dry THF (38 liters) at constant stirring at 25° C. for12 hours or until the polymer is dissolved. A slurry of 2.96 mole (260grams) of potassium thioacetate, was prepared with one (1) liter of dryTHF. The slurry was added to the polymer solution slowly, with constantstirring. The reaction mixture was held at 25° C. for 24 hours. At theend of the stipulated time, the reaction mixture is introduced into thequench pot containing 100 liters of isopropanol, to precipitate thefunctionalized polymer. The polymer was re-dissolved in a reactorcontaining 20 liters of isohexane and 2 wt % of butylated hydroxytoluene(BHT; Sigma Aldrich). The re-dissolved polymer was introduced into the50 liters steam stripping pot, connected with a condenser and a chiller.The steam stripping is done using 20 kilograms per hour of steam undernitrogen blanket. The steam stripped functionalized polymer was finallydried using heated roll mill to obtain 4200 grams of functionalizedEXXPRO™. The dried polymer was characterized using proton NMRspectroscopy & FTIR showing compete conversion in 24 hours. As shown inFIG. 1, 1H NMR spectroscopy shows complete disappearance of methyleneproton (˜CH2Br), with new resonance appearing at 4.09 ppm for˜CH₂S—COCH₃.

Example 2

Cure Behavior of Rubber Compositions without Fillers

20 grams of polymer sample of BIMSM elastomer (EXXPRO-NPX1602,Experimental product from ExxonMobil Chemical) or thioacetatefunctionalized poly(isobutylene-co-para-methylstyrene) was obtained fromExample 1 and pressed between two Teflon sheets in a Carver press at 50°C.

The following curatives were used: 1 to 4 phr of tetramethylthiuramdisulfide (TMTD), 2 phr of dipentamethylenethiuram tetrasulfide (DPTT),2.3 phr of N-cyclohexyl-benzothiazole sulfonamide (CBS) and 2.3 phr ofdiphenylguanidine (DPG) Each curative was added to the polymer sheet,followed by repeated folding and pressing approximately 10 times to mixand disperse the curatives into the polymer sample. The cure behavior ofeach of the samples was studied using Moving Die Rheometer (MDR) at at160° C. and 1° arc for 30 or 40 minutes. The formulation and MDR dataare summarized in the Tables 1A and 1B immediately below. All componentsare listed in phr, or part per hundred, of polymer unit.

TABLE 1A MDR Data for Unfilled Compositions of BIMSM and UnfilledZinc-Free Compositions of FunctionalizedPoly(isobutylene-co-para-methylstyrene) Example Example Example ExampleFormulation (phr) 2A 2B 2C 2D BIMSM 100 100 100 (Exxpro NPX 1602)Thioacetate 100 functionalized poly(isobutylene- co-para-methylstyrene)tetramethylthiuram 2 1 disulfide (TMTD) dipentamethylenethiuram 2tetrasulfide (DPTT) N-cyclohexyl- 2.3 + 2.3 benzothiazole sulfonamide(CBS) + diphenylguanidine (DPG) Total phr 102 102 104.6 101 MDR @160° C.for 30 or 40 min ML (dN · m) 2.28 1.34 1.88 1.67 MH (dN · m) 2.9 2.85.91 6.78 MH − ML (dN · m) 0.62 1.46 4.03 5.11 ts2 (min) N/A N/A 3.885.2 t90 (min) 0.11 0.11 8.45 14.41

TABLE 1B MDR Data for Unfilled Compositions of BIMSM and UnfilledZinc-Free Compositions of FunctionalizedPoly(isobutylene-co-para-methylstyrene Example Example Example ExampleFormulation (phr) 2E 2F 2G 2H Thioacetate 100 100 100 100 functionalizedpoly(isobutylene- co-para-methylstyrene) tetramethylthiuram 2 4disulfide (TMTD) dipentamethylenethiuram 2 tetrasulfide (DPTT)N-cyclohexyl- 2.3 + 2.3 benzothiazole sulfonamide (CBS) +diphenylguanidine (DPG) Total phr 102 104 102 100 MDR @160° C. for 30 or40 min ML (dN · m) 1.9 1.5 2.05 1.77 MH (dN · m) 10.03 12.6 7.12 9.1 MH− ML (dN · m) 8.13 11.1 5.07 7.33 ts2 (min) 4.88 4.99 6.02 4.86 t90(min) 9.94 10.99 10.3 14.95

Example 3 Cure Behavior of Rubber Compositions Comprising Fillers

All rubber compositions were prepared by one-step mixing in a laboratoryBrabender mixer equipped with a cam type-mixing head. All compoundingredients, including rubber and curatives, were added into thepreheated mixing chamber and mixed for 6 min at 35 rpm and a startingtemperature of 75° C. The formulation and relevant compositionproperties of rubber compositions 3 A through 3J are summarized inTables 2A, 2B and 2C. Each of the components are listed in phr, or partper hundred, of polymer unit.

Stress/Strain Measurements

Five test specimens were dies out with ASTM D4482 die and conditioned inthe lab for 16 hours before testing.

Specimens were tested on an Instron 5565 with a long travel mechanicalextensometer.

The load cell and extensometer are calibrated before each day oftesting. Extensometer is calibrated @ 20 mm as gauge length.

Sample information, operator name, date, lab temperature, and humidityare all recorded.

Specimen thickness was measured at three places in the test area. Theaverage value was entered when prompted. The lab temperature andhumidity are measured.

Specimen was carefully loaded in the grips to ensure grips clamp on thespecimen symmetrically. The extensometer grips was then attached to thesample in the test area.

The test was prompted to start. A pre-load of 0.1N was applied. Testingbegan with the crosshead moving at 20 inches/minute until a break isdetected.

Five specimens from each sample were tested and the median values wereused for reporting.

TABLE 2A MDR and Tensile Data for Filled Compositions of BIMSM andFilled Compositions of FunctionalizedPoly(isobutylene-co-para-methylstyrene) Example Example ExampleFormulation (phr) 3A 3B 3C BIMSM 100 100 (Exxpro NPX 1602) Thioacetate100 functionalized poly(isobutylene- co-para-methylstyrene) Carbon black(N330) 20 20 Silica (Agilon 454) 20 tetramethylthiuram disulfide (TMTD)dipentamethylenethiuram 2 2 2 tetrasulfide (DPTT) Sulfur Total phr 122122 122 MDR @160° C. for 30 or 40 min ML (dN · m) 3.56 5.21 3.32 MH (dN· m) 4.87 8.98 14.29 MH − ML (dN · m) 1.31 3.77 10.97 ts2 (min) N/A 0.112.70 t90 (min) 0.1 35.53 5.19 Tensile Modulus @ 100% [Mpa] 4.546 1.014.639 Modulus @ 200% [Mpa] 4.878 1.43 6.011 Modulus @ 300% [Mpa] 5.1821.84 8.174 Ultimate tensile (Mpa) 3.74 3.19 18.2 Elongation at break (%)1702 1035 610

TABLE 2B MDR and Tensile Data for Filled Compositions of BIMSM andFilled Compositions of FunctionalizedPoly(isobutylene-co-para-methylstyrene) Example Example ExampleFormulation (phr) 3D 3E 3F Thioacetate 100 100 100 functionalizedpoly(isobutylene- co-para-methylstyrene) Carbon black (N330) 60 8 Silica(Agilon 454) 20 tetramethylthiuram 2 2 disulfide (TMTD)dipentamethylenethiuram 2 tetrasulfide (DPTT) Sulfur Total phr 122 162110 MDR @160° C. for 30 or 40 min ML (dN · m) 3.91 4.42 2.46 MH (dN · m)15.66 29.85 13.57 MH − ML (dN · m) 11.75 25.43 11.11 ts2 (min) 0.12 1.923.56 t90 (min) 16.23 8.21 8.20 Tensile Modulus @ 100% [Mpa] 1.11 3.540.76 Modulus @ 200% [Mpa] 2.06 8.48 1.59 Modulus @ 300% [Mpa] 3.20 13.433.33 Ultimate tensile (Mpa) 7.63 15.00 4.90 Elongation at break (%) 565341 360

TABLE 2C MDR and Tensile Data for Filled Compositions of BIMSM andFilled Compositions of FunctionalizedPoly(isobutylene-co-para-methylstyrene) Example Example Example ExampleFormulation (phr) 3G 3H 31 3J Thioacetate 100 100 100 100 functionalizedpoly(isobutylene- co-para-methylstyrene) Carbon black (N330) 8 8 Silica(Agilon 454) 8 8 tetramethylthiuram 2 2 disulfide (TMTD)dipentamethylenethiuram 2 2 tetrasulfide (DPTT) Sulfur 1 Total phr 110110 110 111 MDR @160° C. for 30 or 40 min ML (dN · m) 2.50 2.54 2.581.93 MH (dN · m) 9.85 12.36 11.21 13.72 MH − ML (dN · m) 7.35 9.82 8.6311.79 ts2 (min) 3.88 2.04 2.66 2.97 t90 (min) 6.71 4.15 5.75 6.45Tensile Modulus @ 100% [Mpa] 0.57 0.73 0.71 0.78 Modulus @ 200% [Mpa]0.95 1.36 1.23 1.56 Modulus @ 300% [Mpa] 1.60 2.40 2.02 3.03 Ultimatetensile (Mpa) 5.94 3.22 4.86 6.10 Elongation at break (%) 583 354 471456

The present thioacetate isobutylene-based polymers are useful inpharmaceutical applications, and tire applications as rubbercompositions with the use of EV or semi-EV vulcanizations systems. Thesubject rubber compositions comprise thioalkylated functionalizediso-butylene based polymer and a sulfur donor and/or accelerator curesystem as described above. These zinc-free rubber compositions furthercomprise one or more hydrocarbon resins and a filler as described above.

As used herein, hydrocarbon resins include aliphatic hydrocarbon resins,cyclic aliphatic hydrocarbon resins, modified aliphatic hydrocarbonresins, aromatic hydrocarbon resins, modified aromatic hydrocarbonresins, cyclopentadiene-based resins (including but not limited topolycyclopentadiene resins, hydrogenated polycyclopentadiene resins,etc.), gum rosins, gum rosin esters, wood rosins, wood rosin esters,tall oil rosins, tall oil rosin esters, polyterpenes, aromatic modifiedpolyterpenes, terpene phenolics, aromatic modified hydrogenatedpolycyclopentadiene resins, hydrogenated aliphatic resin, hydrogenatedaliphatic aromatic resins, hydrogenated terpenes, modified terpenes,hydrogenated rosin acids, hydrogenated rosin acids, hydrogenated rosinesters, derivatives thereof and/or combinations thereof. Such resins andmethods for making them have been described in, for example, U.S. Pat.Nos. 4,629,766; 5,874,512; 6,232,418; 6,455,652; and 6,992,131.

The hydrocarbon resin may be a modified hydrocarbon resin and can havesoftening points of greater than 80° C., greater than 85° C., greaterthan 90° C., greater than 92° C., greater than 95° C., greater than 100°C., greater than 110° C., greater than 120° C., greater than 135° C.,greater than 140° C., greater than 145° C., greater than 150° C., orgreater than 160° C., as measured by ASTM D 6090-97. Alternativelystated, the hydrocarbon resin and modified hydrocarbon resin may havesoftening points of from 80° C. to 160° C., 82° C. to 140° C., 85° C. to130° C., 90° C. to 125° C., 95° C. to 120° C., or 95° C. to 140° C., asmeasured by ASTM D 6090-97.

The hydrocarbon resin and modified hydrocarbon resin can also have anaromaticity (% aromatic protons) of 15% or less, 12% or less, 8% orless, 6% or less, 4% or less, or 2% or less. Alternatively stated, thehydrocarbon resin and modified hydrocarbon resin may have an aromaticity(% aromatic protons) of from 1 to 15%, 1 to 12%, 1 to 10%, 1 to 8%, 2 to6%, or 2 to 4%.

Suitable hydrocarbon resins in the subject zinc-free rubber compositionsinclude, but are not limited to, available Escorez™ resins, for example,ESCOREZ™ resins 1000, 2000, and 5000 series, from ExxonMobil ChemicalCompany, Houston, Tex. By way of example, ESCOREZ™ 1102 refers to analiphatic hydrocarbon resin having a softening point of 212 F, a meltviscosity of 1650 cP, a molecular weight-number average (Mn) of 1300g/mol and a molecular weight−weight average (Mw) of 2900 g/mol useful toincrease tack and adhesive properties and modify mechanical and opticalproperties of polymer blends and thermally polymerized.

ESCOREZ™ 2520 refers to a petroleum hydrocarbon tackifier resin havingC5-C6 olefins and diolefins as major components and thermallypolymerized.

ESCOREZ™ E5000 refers to a petroleum hydrocarbon tackifier resin havingpolycyclodienes (C10-C12 cyclodiene dimers plus dicyclopentadiene withor without C8-C10 vinyl aromatics) as a major component which isthermally polymerized.

The phrases, unless otherwise specified, “consists essentially of” and“consisting essentially of” do not exclude the presence of other steps,elements, or materials, whether or not, specifically mentioned in thisspecification, so long as such steps, elements, or materials, do notaffect the basic and novel characteristics of the invention,additionally, they do not exclude impurities and variances normallyassociated with the elements and materials used.

For the sake of brevity, only certain ranges are explicitly disclosedherein. However, ranges from any lower limit may be combined with anyupper limit to recite a range not explicitly recited, as well as, rangesfrom any lower limit may be combined with any other lower limit torecite a range not explicitly recited, in the same way, ranges from anyupper limit may be combined with any other upper limit to recite a rangenot explicitly recited. Additionally, within a range includes everypoint or individual value between its end points even though notexplicitly recited. Thus, every point or individual value may serve asits own lower or upper limit combined with any other point or individualvalue or any other lower or upper limit, to recite a range notexplicitly recited.

All priority documents are herein fully incorporated by reference forall jurisdictions in which such incorporation is permitted and to theextent such disclosure is consistent with the description of the presentinvention. Further, all documents and references cited herein, includingtesting procedures, publications, patents, journal articles, etc. areherein fully incorporated by reference for all jurisdictions in whichsuch incorporation is permitted and to the extent such disclosure isconsistent with the description of the present invention.

While this teaching has been described with respect to a number ofaspects and examples, those skilled in the art, having benefit of thisdisclosure, will appreciate that other aspects can be devised which donot depart from the scope and spirit of the inventions disclosed herein

1. A thioacetate isobutylene-based polymer composition comprising (a) athioalkylated functionalized polymer; and (b) one of or a combination ofany of the following: (i) a sulfur donor; (ii) a blend of sulfur and asulfur donor; and (iii) an accelerator cure system.
 2. The thioacetateisobutylene-based polymer composition of claim 1, wherein thefunctionalized polymer is thioacetate functionalizedpoly(isobutylene-co-para-methylstyrene).
 3. The thioacetateisobutylene-based polymer composition of claim 1, further comprising atleast one filler.
 4. The thioacetate isobutylene-based polymercomposition of claim 1, wherein the sulfur donor is selected from thegroup consisting of tetramethyl thiuram disulfide (“TMTD”),4,4′-dithiodimorpholine, dipentamethylene thiuram tetrasulfide (“DPTT”),and thiocarbamyl sulfonamide.
 5. The thioacetate isobutylene-basedpolymer composition of claim 1, wherein the accelerator cure systemcomprises one or more of thiazoles, amines, guanidines, sulfenamides,thiurams, dithiocarbamates, and/or zanthates.
 6. The thioacetateisobutylene-based polymer composition of claim 5, wherein theaccelerator cure system is N-cyclohexyl-2-benzothiazole sulfenamide(“CBS”) or diphenylguanidine (“DPG”).
 7. The thioacetateisobutylene-based polymer composition of claim 3, wherein the filler isselected from the group consisting of carbon black, white filler, andcombinations thereof.
 8. The thioacetate isobutylene-based polymer ofclaim 1, wherein the composition is useful as a thermoset inpharmaceutical and tire applications.
 9. A thermoset compositioncomprising: (a) a thioalkylated functionalized polymer; and (b) one ofor a combination of any of the following: (i) a sulfur donor; (ii) ablend of sulfur and a sulfur donor; and (iii) an accelerator curesystem; wherein the composition is substantially free of zinc.
 10. Thethermoset composition of claim 9, wherein the functionalized polymer isthioacetate functionalized poly(isobutylene-co-para-methylstyrene). 11.The thermoset composition of claim 9, further comprising at least onefiller.
 12. The thermoset composition of claim 11, wherein the filler isselected from the group of carbon black, white filler, and combinationsthereof.
 13. The thermoset composition of claim 9, wherein theaccelerator cure system is N-cyclohexyl-2-benzothiazole sulfenamide(“CBS”) or diphenylguanidine (“DPG”).
 14. The thermoset composition ofclaim 9, wherein the sulfur donor is selected from the group consistingof tetramethyl thiuram disulfide (“TMTD”), 4,4′-dithiodimorpholine,dipentamethylene thiuram tetrasulfide (“DPTT”), and thiocarbamylsulfonamide.
 15. A rubber composition comprising the thermosetcomposition of claim
 1. 16. The rubber composition of claim 15 furthercomprising a hydrocarbon resin.
 17. The rubber composition of claim 16,wherein the hydrocarbon resin is hydrogenated.
 18. The rubbercomposition of claim 15, wherein the hydrocarbon resin comprisescyclopentadiene, dicyclopentadiene, methylcyclopentadiene, andcombinations thereof.
 19. An article comprising the rubber compositionof claim 15.